Post_1_5.cs

public override void Configure(IApplicationBuilder applicationBuilder)
{
  if (this.serviceProvider.GetService<IHostingEnvironment>().IsDevelopment())
  {
    applicationBuilder.UseDeveloperExceptionPage();
    applicationBuilder.UseBrowserLink();
  }

  base.Configure(applicationBuilder);
  applicationBuilder.Run(async (context) =>
  {
    await context.Response.WriteAsync(ExtensionManager.Extensions.First().Name);
  });
}